Belt Tensioner - Excessive Movement?
 

I replaced the belt on my 2011 X5 with the N55. While watching it run, the belt tensioner seemed to bounce around/move a lot! I have a video link below, but the tensioner was moving so fast, the frame rate didn't capture all of the movement. I replaced the belt tensioner a couple of years ago with an OEM supplier INA one. I can't recall watching it at that time (I should have so I had a baseline). Is this normal? I've never seen this much movement in a belt tensioner. What does your belt tensioner look like while running? Thanks.

Video:
https://youtu.be/A4fwgwOvscA

Mine did that after a belt disintegrated. Was pieces of belt in the baby v groves.

Andrew, do you think your tensioner was the root cause of the belt disintegrating? Did you replace your tensioner soon after putting on the new belt? If not, I assume it has been good for you for awhile now?

I would replace both without delay, belt and tensioner, maybe pulleys too. Risk of serious or even catastrophic damage from slipping off or disintegrating belt while driving, low cost of repair if you do it yourself

OFHG leak but the tensioner was shot and not straight anymore.

Get a front seal shield! I didn't and my belt took out the seal! I was lucky that it happened on a short drive and didn't suck the belt into the engine.

Great design on the fms was not difficult but you don't want to go though that trust me!

I second replacing it. While there is some movement even with a brand new tensioner at idle this is way more excessive than it should be.

The tensioner is not the root of the problem. it's moving to compensate for something else. By the frequency I would say more to do with the belt.

Thank you all for your replies. The spring on the tensioner could be weak, so I'll replace it.

@80stech, the belt is brand new and I checked the idler pulleys when replacing the belt and they felt fine. I also checked the AC pulley, power steering pulley, and alternator pulley. Could be drag on the AC compressor when engage?

It looks like it is moving in time with the belt so maybe try a different belt.

Did you fixed the problem yet?

That does not look Ok! I replaced the belt, tensioner and both of the guiding wheels last week, runs normal.
Also noticed that I have a leaking OFHG, when replacing the belt I could feel on the old belt that is was deteriating.

So I would remove the belt again, check the groves on the belt, check the tread on all the Pulleys, there good be some stuff in the groves, also check the 2 guiding weels on good rolling and no play.

Drag from the AC turning on and off, has not that frequentie.